This invention relates generally to electrical connectors, and more particularly, to power utility connectors for mechanically and electrically connecting a tap or distribution conductor to a main electrical transmission conductor.
Electrical utility firms constructing, operating and maintaining overhead and/or underground power distribution networks and systems utilize connectors to tap main power transmission conductors and feed electrical power to distribution line conductors, sometimes referred to as tap conductors. The main power line conductors and the tap conductors are typically high voltage cables that are relatively large in diameter, and the main power line conductor may be differently sized from the tap conductor, requiring specially designed connector components to adequately connect tap conductors to main power line conductors. Generally speaking, three types of connectors are commonly used for such purposes, namely bolt-on connectors, compression-type connectors, and wedge connectors.
Bolt-on connectors typically employ die-cast metal connector pieces or connector halves formed as mirror images of one another, sometimes referred to as clam shell connectors. Each of the connector halves defines opposing channels that axially receive the main power conductor and the tap conductor, respectively, and the connector halves are bolted to one another to clamp the metal connector pieces to the conductors. Such bolt-on connectors have been widely accepted in the industry primarily due to their ease of installation, but such connectors are not without disadvantages. For example, proper installation of such connectors is often dependent upon predetermined torque requirements of the bolt connection to achieve adequate connectivity of the main and tap conductors. Applied torque in tightening the bolted connection generates tensile force in the bolt that, in turn, creates normal force on the conductors between the connector halves. Applicable torque requirements, however, may or may not be actually achieved in the field and even if the bolt is properly tightened to the proper torque requirements initially, over time, and because of relative movement of the conductors relative to the connector pieces or compressible deformation of the cables and/or the connector pieces over time, the effective clamping force may be considerably reduced. Additionally, the force produced in the bolt is dependent upon frictional forces in the threads of the bolt, which may vary considerably and lead to inconsistent application of force among different connectors.
Compression connectors, instead of utilizing separate connector pieces, may include a single metal piece connector that is bent or deformed around the main power conductor and the tap conductor to clamp them to one another. Such compression connectors are generally available at a lower cost than bolt-on connectors, but are more difficult to install. Hand tools are often utilized to bend the connector around the cables, and because the quality of the connection is dependent upon the relative strength and skill of the installer, widely varying quality of connections may result. Poorly installed or improperly installed compression connectors can present reliability issues in power distribution systems.
Wedge connectors are also known that include a C-shaped channel member that hooks over the main power conductor and the tap conductor, and a wedge member having channels in its opposing sides. The wedge member is driven through the C-shaped member, deflecting the ends of the C-shaped member and clamping the conductors between the channels in the wedge member and the ends of the C-shaped member. An application tool is used to drive the wedge member to a proper position with respect to the channel member to achieve a repeatable, consistent connection with the conductors. One such wedge connector is commercially available from Tyco Electronics Corporation of Harrisburg, Pa. and is known as an AMPACT Tap or Stirrup Connector. AMPACT connectors include different sized channel members to accommodate a set range of conductor sizes, and multiple wedge sizes for each channel member. Each wedge accommodates a different conductor size. As a result, AMPACT connectors tend to be more expensive than either bolt-on or compression connectors due to the increased part count. For example, a user may be required to possess three channel members that accommodate a full range of conductor sizes. Additionally, each channel member may require up to five wedge members to accommodate each conductor size for the corresponding channel member. As such, the user must carry fifteen connector pieces in the field to accommodate the full range of conductor sizes. The increased part count increases the overall expense and complexity of the AMPACT connectors.
AMPACT connectors are believed to provide superior performance over bolt-on and compression connectors. For example, the AMPACT connector results in a wiping contact surface that, unlike bolt-on and compression connectors, is stable, repeatable, and consistently applied to the conductors, and the quality of the mechanical and electrical connection is not as dependent on torque requirements and/or relative skill of the installer. Additionally, and unlike bolt-on or compression connectors, because of the deflection of the ends of the C-shaped member some elastic range is present wherein the ends of the C-shaped member may spring back and compensate for relative compressible deformation or movement of the conductors with respect to the wedge and/or the C-shaped member.
It would be desirable to provide a lower cost, more universally applicable alternative to conventional wedge connectors that provides superior connection performance to bolt-on and compression connectors.